Re: unknown devices in JTAG chain

Kay,

I assume that you were using initialize chain to detect the devices. I 
also assume that you're using 6.1isp2 iMPACT to perform configuration. 
When iMPACT performs chain initialization, only TMS and TCK are toggled. 
Take a look at Xilinx soln 11857.

So if the chain isn't detected correct, you'll want to probe the TMS, 
TCK, and TDO pins of each device. (ie. are the pins connected correctly, 
anything shorted, etc...)

Other possible causes includes board SI, parallel port noise. You may 
want to contact the Xilinx hotline support for further help.

Regards, Wei

Kay Schubert wrote:
> Hi,
>
> I designed a FPGA prototyping board with a Spartan XC2S200E and a XC18V02
> PROM.
> To configure these devices I put a JTAG header on the board and routed it as
> described in
> the following Xilinx datasheet:
> http://toolbox.xilinx.com/docsan/xilinx4/data/docs/pac/designing7.html
>
> At the software-side I use impact and the PC3 from Xilinx. When I start
> impact in boundary-scan mode,
> the PC3 will be detected (as [EMAIL PROTECTED]) and  the boundary-scan chain will
> be identified. But there's the problem:
> impact always detects 11 devices in the chain, but there are only two.
> And: Even though the two devices are original Xilinx parts, no ID codes were
> returned (or better: the returned codes
> don't match with Xilinx parts).
>
> I checked the configuration connections and the power supply, but
> everything seems to be o.k. Has anybody of you an idea what the problem
> could be?
>
> thanks, Kay